1. Field of the Invention
The present invention relates to an imaging apparatus, element, and image processing method.
2. Description of the Related Art
FIG. 29 is a diagram illustrating a two-dimensionally arranged pixel group of a conventional solid-state imaging element. As illustrated in FIG. 29, in a two-dimensionally arranged pixel group 2901, primary color (RGB) separating filters are arranged respectively on pixels in a Bayer arrangement.
According to a conventional technique in Japanese Patent Application Laid-Open Publication No. 2003-318375, a solid-state imaging element is disclosed that captures an image having brightness resolution that is not influenced by color information of the subject. The solid-state imaging element includes photodiodes arranged horizontally and vertically. Brightness filters Y are provided for photodiodes that are arranged in checkers of the photodiodes. Color filters R, G, and B are provided for the remaining photodiodes that are arranged in checkers and not provided with brightness filters Y.
According to another conventional technique in Japanese Patent Application Laid-Open Publication No. 2003-244712, an imaging element is disclosed that includes pixels arranged in a pattern similar to the Bayer arrangement shown in FIG. 29. The pixel arrangement of this imaging element differs from the Bayer arrangement shown in FIG. 29 in that the pixel arrangement has fewer “G” pixels. Therefore, normally, when an image is captured, a color difference signal is produced using pixel outputs of “R”, “G”, and “B” and a brightness signal is produced using pixel output of pixels on which no color filters are formed.
However, recently, reduced camera size along with increased pixels has been demanded. Therefore, in the above mentioned solid-state imaging element employing the Bayer arrangement shown in FIG. 29, the area per one pixel is decreased due to the reduced camera-size and increased pixels therein and, simultaneously, the area of the photodiode decreases. Therefore, a problem of insufficient sensitivity has arisen. In particular, the color specific separating filters cause reduced sensitivity by weakening the brightness component of incoming visual light because each color separating filter only transmits the frequency component of the color that respectively corresponds thereto.
According to the conventional technique in Japanese Patent Application Laid-Open Publication No. 2003-318375, a problem arises in that, while the brightness resolution which is not influenced by the color information of the subject is improved, the resolution of the color information (color difference) obtained is degraded to one half of the original value when lighting is bright.
According to the conventional technique in Japanese Patent Application Laid-Open Publication No. 2003-244712, because the color difference signal is produced using the. RGB pixel output, while the color resolution is improved when lighting is bright, only one pixel of four pixels does not have a color separation filter formed thereon. Therefore, a problem arises in that the brightness resolution obtained is degraded when lighting is bright.
To solve the problems arising with the above conventional techniques, an object of the present invention is to provide an imaging apparatus, an imaging element, and an image processing method, that can facilitate improvement of the image quality of images captured regardless of whether lighting is bright or dim, by achieving high-resolution brightness when lighting is bright and high sensitivity when lighting is dim.